Which of the following is a specimen type for hematology?

Venous blood is the specimen type for hematology because hematology primarily involves the study of blood and its components, including red blood cells, white blood cells, and platelets. This type of analysis is crucial for diagnosing and monitoring various blood disorders such as anemia, leukemias, and clotting problems.

In hematology, venous blood is commonly collected via venipuncture, allowing for accurate and reliable evaluations of blood cell counts and other parameters. The other options, while valuable specimens in their own right, are not typically associated with hematological analyses. Saliva is used in tests for various conditions, usually focusing on hormonal or microbial analyses; urine is primarily examined for metabolic and kidney function tests; and tissue biopsies are typically analyzed in pathology rather than hematology. Thus, venous blood stands out as the key specimen for hematological investigations.